<p>The low-temperature states of Sr<InlineEquation ID="IEq7"> <EquationSource Format="TEX">$_{1-x}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow> <mn>1</mn> <mo>-</mo> <mi>x</mi> </mrow> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>Ca<InlineEquation ID="IEq8"> <EquationSource Format="TEX">$_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mi>x</mi> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>TiO<InlineEquation ID="IEq9"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> exhibit intriguing dielectric properties with increasing Ca substitution. Pure SrTiO<InlineEquation ID="IEq10"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> is a quantum paraelectric. However, a slight Ca doping induces a quantum ferroelectric state. Additionally, a relaxor-like state emerges when the Ca concentration exceeds <InlineEquation ID="IEq11"> <EquationSource Format="TEX">$x = 0.016$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>=</mo> <mn>0.016</mn> </mrow> </math></EquationSource> </InlineEquation>, characterized by rounded and diffused peaks in the dielectric constant. This phenomenon is attributed to local polarizations resulting from structural disorder. We performed neutron total scattering measurements on Sr<InlineEquation ID="IEq12"> <EquationSource Format="TEX">$_{1-x}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow> <mn>1</mn> <mo>-</mo> <mi>x</mi> </mrow> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>Ca<InlineEquation ID="IEq13"> <EquationSource Format="TEX">$_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mi>x</mi> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>TiO<InlineEquation ID="IEq14"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq15"> <EquationSource Format="TEX">$x=0, 0.06, 0.1$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mn>0.06</mn> <mo>,</mo> <mn>0.1</mn> </mrow> </math></EquationSource> </InlineEquation>) at 15 K to investigate the structural origin of these relaxor-like behaviors. Using Rietveld refinements, we discussed that Ca substitution intensifies the antiferrodistortive octahedral rotations. Local structural distortions were further studied through reverse Monte Carlo modeling, revealing that Sr/Ca-O bond length distributions become broader and more asymmetric with increasing Ca concentration. We propose that octahedral rotational disorders, dependent on local Sr/Ca configurations, are responsible for the asymmetry in Sr/Ca-O bond length distributions and the induction of local polarizations.</p>

Neutron total scattering and reverse Monte Carlo study of structural disorder in Sr$_{1-x}$Ca$_{x}$TiO$_3$

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发表日期：

2025年10月6日

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I.-K. Jeong

摘要

The low-temperature states of Sr $_{1-x}$ $_{1 - x}$ Ca $_{x}$ $_{x}$ TiO $_3$ $_{3}$ exhibit intriguing dielectric properties with increasing Ca substitution. Pure SrTiO $_3$ $_{3}$ is a quantum paraelectric. However, a slight Ca doping induces a quantum ferroelectric state. Additionally, a relaxor-like state emerges when the Ca concentration exceeds $x = 0.016$ $x = 0.016$ , characterized by rounded and diffused peaks in the dielectric constant. This phenomenon is attributed to local polarizations resulting from structural disorder. We performed neutron total scattering measurements on Sr $_{1-x}$ $_{1 - x}$ Ca $_{x}$ $_{x}$ TiO $_3$ $_{3}$ ( $x=0, 0.06, 0.1$ $x = 0, 0.06, 0.1$ ) at 15 K to investigate the structural origin of these relaxor-like behaviors. Using Rietveld refinements, we discussed that Ca substitution intensifies the antiferrodistortive octahedral rotations. Local structural distortions were further studied through reverse Monte Carlo modeling, revealing that Sr/Ca-O bond length distributions become broader and more asymmetric with increasing Ca concentration. We propose that octahedral rotational disorders, dependent on local Sr/Ca configurations, are responsible for the asymmetry in Sr/Ca-O bond length distributions and the induction of local polarizations.

Neutron total scattering and reverse Monte Carlo study of structural disorder in Sr\(_{1-x}\)Ca\(_{x}\)TiO\(_3\)

摘要